Optical systems of this type are used, for example, for so-called sun simulators, that is, test equipment in which space missiles are subjected to artificially created space conditions, including an intense, single-sided radiant flux corresponding to solar radiation.
To generate the necessary high-radiation intensity, a plurality of high-power lamps are placed in a row and supply a light flux corresponding to a power of several 100 kw. This light flux is directed onto the test object via an integrator assembly made up of an array of field lenses arranged side-by-side and an identical arrangement of projection lenses as well as via a collimator mirror mounted in the interior of the evacuated test chamber. In this arrangement, the collimator mirror is usually positioned to reflect the beam off-axis which beam arrives from the integrator, that is, the beam is reflected at an angle to its axis of symmetry.
As a result of this arrangement, the collimator mirror transforms the circular-conical beam of the state-of-the-art emanating from the integrator into a beam of elliptical cross section. The light outside the given usable region of the test plane is lost and has to be removed by costly cooling equipment. On the other hand, this part of the radiation is missing in the test plane.